To start things off, I'm not the actual Administrator for the VPN Server, but he is also at a loss so I thought I'd ask it here. I know it's a Cisco ASA Firewall/VPN.
I have a router that connects to the Cisco VPN server, it does so succesfully. I can ping everything within the remote network and from the remote network into my own. I've been able to SSH into a remote server over VPN as well, it all seems to work; until there's some more data returned.
A quick example would be an internal webserver. The default homepage simply redirects, so only sends back HTTP headers with a "Location:". I receive this on my computer, but when I request the actual page then (which isn't that big) I don't get a response at all - it just stalls. And it does this for other services as well, for example SSH. I can do a couple of things while connected, but if there's more than xx output it seems to do nothing. The connection remains active throughout all of this.
Has anyone ever experienced anything like this before / know what the problem might be? Another user who has a site-to-site connection with this VPN using the -exact same setup- has no problems, the only difference is that I have around 200ms ping to the VPN server/network because of a very long distance (other continent).
Problem solved: turned out the MTU from my ISP was lower, and unchangable according to the ISP "tech guy". So, we just lowered it on my end / vpn and it works purrfectly now.